The cytotoxic activity of the polymer-copper(II) complex, [Cu(bpy)(2)(BPEI)]Cl-2 center dot 4H(2)O (bpy = 2,2'-bipyridine, BPEI = branched polyethyleneimine) on NCI-H460 human lung cancer cells was determined adopting MTT assay and specific staining techniques. Many of the cultured NCI-H460 cancer cells treated with this complex suffered loss of viability and death mostly through apoptosis and/or necrosis as evidenced by the changes in the nuclear morphology and cytoplasmic features.